John Docherty, 49, was today found guilty of killing the teenager as she was returning home from a disco in the town.

During the 50-day trial, prosecutors said Docherty, of Dunoon, Argyll and Bute, forced her to the ground and killed her. She had been strangled.

He denied the charges, claiming someone else was responsible, but jurors at the High Court in Edinburgh convicted him of the murder by a majority verdict.

Elaine was last seen alive by two friends after she left the disco in the town's Laird Street on June 1, 1986.

Her body was found the next day in a lane off Ardgowan Street.

The prosecution was the first to go to court following an investigation by the Crown Office's cold case unit, which was set up in 2011.

Strathclyde Police launched a fresh appeal over her death and Docherty was arrested in March last year.

He was charged with attacking her and removing her clothes before forcing her to the ground and placing a ligature around her neck and strangling her.

He denied the charges and lodged special defences of alibi and incrimination.

But after evading justice for nearly 30 years, jurors today found him guilty of the crime.

In a statement released through Police Scotland after the conviction, the teenager's mother Maureen Doyle thanked officers and staff who had worked on the inquiry for the past 28 years.

She said: " Particular thanks must also go to Mr Frank Mulholland, the Lord Advocate, who was kind to my late husband, Jack, when he met him three years ago and who has followed the progress of the inquiry since 1986, and Mr John Scullion, for prosecuting the case at court. The people of Inverclyde who have lived this nightmare with us for the last 28 years and have always supported our family.

"The result at court doesn't make our day to day living any easier - the pain doesn't go away, but my son John and I take comfort that we now have justice for Elaine, which is all we, especially her dad Jack, campaigned for."

The case, which featured on the BBC Crimewatch programme three years ago, was one of the country's longest-running unsolved murders and had "cast a long shadow" over the town.

Police spoke to thousands of people during the inquiry over three decades but it was advances in forensic science which helped catch her killer when evidence was examined 20 years later.

DNA found on Elaine's back matched a profile for DNA found on her face.

Former soldier Docherty provided a DNA sample voluntarily in May 2012 and it was a one in a billion match.

Detective Superintendent Bobby Hendren said he was " extremely pleased" with today's verdict.

"This investigation has always been about Elaine Doyle and her family and bringing the man responsible for her murder to trial", he said.

"I would like to pay tribute to her mum and brother who have continued to support us throughout this investigation and I am sorry that her dad is no longer with us to hear the verdict.

"I can only hope that today's verdict brings them some comfort."

He added: "I would also like to thank the people of Greenock for their continued help and support in the past 28 years. I, and all the officers who worked on this investigation, are well aware that the senseless murder of Elaine has cast a long shadow over the town of Greenock and we would not be where we are today without their support.

"I would also like to take this opportunity to thank the Scottish Police Authority Forensic Scientists for their help. They have continually looked for new ideas and new ways of working to help this investigation. Their support was vital in bringing John Docherty to justice."